I don't know which churches are available where you are from, but from my own experiences, I'd say that mass itself offers does not offer much interaction as everyone is focussed on the priest and his sermon (which I don't want to portray as a bad thing, by the way). But after mass, people often take some time to break up the gathering, say their good-byes to each other, in some places it's even usual to talk for a while with others about the mass or with the priest about things that one is troubled by at the moment.
There is other gatherings organized by the various churches that may be more like what you are looking for. In many places there is community gatherings where some sub-faction of the community comes together and interacts. For example, elderly people might be invited to regular church coffee meetings or a womens' circle may come together to make things which can be sold at some charity event organized by the church. In many church communities there is information available on which activities they offer, e.g. on their website or in front of their main gathering location. Sometimes people are expected to participate in mass regularly to be accepted into these activities, but in other communities everyone is welcome, though a minor donation to make up for costs or for charity may be welcome.
Instead of joining a church, you could also try to find some other charity organisation that offers regular meetings if you don't feel like attending mass. In many cases the people engaged in charity work are quite open-minded and tolerant and they welcome anybody who's willing to help with their cause. Many meetings that are intended as results-oriented also offer the opportunity for social interaction or at the very least they are slow to break up when they are oficially ended, people instead taking their time and talking about their private life for a bit before they go home. Keeping your eyes open for charity bazaars or other similar events taking place where you live can help you to find one of those groups, as can local newspapers or a quick google search.
Please note that I'm not trying to talk anybody out of attending church, I'm just trying to pint out some additional options that might help the OP find a group they feel comfortable with.
_________________
Yes, I am serious about that avatar...